The present invention relates, in general, to communications, radio wave antennas, and, in particular, to loop type antennas with plural loops.
Antennas for capturing a radio wave are of two basic types: electric field antennas and magnetic field antennas. A fundamental parameter of each type, whether it is a single element or a configuration such as an array, is its sensitivity. A second concern is its frequency range of performance. A third consideration is the spatial pattern of its response to incoming radio waves.
In many applications it is important to measure the direction of arrival of a radio wave. This determination of such a xe2x80x9cline of bearingxe2x80x9d is most often accomplished by using a set of spatially separated elements and properly combining their separate receptions.
According to the book entitled xe2x80x9cAntenna Engineering Handbook, 3rd Ed.,xe2x80x9d edited by Richard C. Johnson, published by McGraw-Hill, Inc. in 1993, pp. 24-8, there are few antenna configurations capable of effective performance in the very low frequency (VLF) range (i.e., 10 KHz to 300 KHz). The most common types are the base-insulated monopole, the top-loaded monopole, the T-antenna, and the inverted-L antenna. The performance of each of these antennas depends on their effective height and volume. In applications where size matters, such antennas may not be practical. In applications where performance matters, these antennas may not perform adequately in the extremely low frequency (ELF) range (i.e., 1 Hz to 10 KHz).
U.S. Pat. No. 3,953,799, entitled xe2x80x9cBROADBAND VLF LOOP ANTENNA,xe2x80x9d discloses a single loop antenna that includes a negative reactance circuit. U.S. Pat. No. 3,953,799 does not disclose the antenna of the present invention and may not operate in the ELF range. U.S. Pat. No. 3,953,799 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 5,357,253, entitled xe2x80x9cSYSTEM AND METHOD FOR EARTH PROBING WITH DEEP SUBSURFACE PENETRATION USING LOW FREQUENCY ELECTROMAGNETIC SIGNALS,xe2x80x9d discloses a single loop antenna for receiving a signal, an amplifier for amplifying the signal, and a combiner for combining the amplified signal with an amplified signal received by a second single loop antenna which is used as a reference. U.S. Pat. No. 5,357,253 does not disclose the antenna of the present invention and may not operate in the ELF range. U.S. Pat. No. 5,357,253 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 5,840,024, entitled xe2x80x9cENDOSCOPE FORM DETECTING APPARATUS IN WHICH COIL IS FIXEDLY MOUNTED BY INSULATING MEMBER SO THAT IT IS NOT DEFORMED WITHIN ENDOSCOPE,xe2x80x9d discloses the use of a three-axes sense coil, but does not disclose the antenna of the present invention and may not operate in the ELF range. U.S. Pat. No. 5,840,024 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 6,084,513, entitled xe2x80x9cMETHOD AND APPARATUS FOR TRACKING A PATIENT,xe2x80x9d discloses a device that uses a loop antenna in each of three axes, but does not disclose the antenna of the present invention and may not operate in the ELF range. U.S. Pat. No. 6,084,513 is hereby incorporated by reference into the specification of the present invention.
U.S. Pat. No. 6,095,260, entitled xe2x80x9cSYSTEM, ARRANGEMENT AND ASSOCIATED METHODS FOR TRACKING AND/OR GUIDING AN UNDERGROUND BORING TOOL,xe2x80x9d THE USE OF A CUBIC ANTENNA,xe2x80x9d discloses the use of a cubic antenna constructed using six circuit boards with spiral conductive patterns formed thereon, but does not disclose the antenna of the present invention and may not operate in the ELF range. U.S. Pat. No. 6,095,260 is hereby incorporated by reference into the specification of the present invention.
It is an object of the present invention to receive a signal with maximum sensitivity.
It is another object of the present invention to receive a signal with maximum sensitivity, where the signal is either a magnetic signal or an electromagnetic signal.
It is another object of the present invention to receive a signal in a compact area.
It is another object of the present invention to determining the line of bearing of a received signal.
It is another object of the present invention to receive a signal with maximum sensitivity by a device with broad instantaneous bandwidth.
The present invention is an antenna that includes a cubic core, having a first axis, a second axis, and a third axis. A first conductor is wound around the first axis of the core a user-definable number of times, or turns, forming a first coil.
A first amplifier is connected to the first coil.
A first dielectric layer surrounds the first coil.
A first electrical shield surrounds the first dielectric layer.
A second dielectric layer surrounds the first electrical shield.
A second conductor is wound around the second dielectric layer in the second axis of the core, forming a second coil.
A second amplifier is connected to the second coil. The second conductor is wound around the second dielectric layer a number of times so that an output voltage of the second amplifier is the same as an output voltage of the first amplifier while under the same signal conditions.
A third dielectric layer surrounds the second coil.
A second electrical shield surrounds the third dielectric layer.
A fourth dielectric layer surrounds the second electrical shield.
A third conductor is wound around the fourth dielectric layer in the third axis, forming a third coil.
A third amplifier is connected to the third coil. The third conductor is wound around the fourth dielectric layer a number of times so that an output voltage of the third amplifier is the same as the output voltages of the first and second amplifiers while under the same signal conditions.
A fifth dielectric layer surrounds the third coil.
A third electrical shield surrounds the fifth dielectric layer.
A sixth dielectric layer surrounds the third electrical shield.
A fifth electrical shield is wrapped around the sixth dielectric layer.
A first anti-aliasing filter is connected to the first amplifier.
A first A/D converter is connected to the first ant-aliasing filter.
A second anti-aliasing filter is connected to the second amplifier.
A second A/D converter is connected to the second ant-aliasing filter.
A third anti-aliasing filter is connected to the third amplifier.
A third A/D converter is connected to the third ant-aliasing filter.
The first, second, and third anti-aliasing filters are connected to a multiplexer.